Instructables
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12v water sensor.bmp
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I will Teach you how to make a simple water sensor circuit
 
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Step 1: Gather Parts

Picture of Gather Parts
Parts List
1 General Purpose NPN Transistor $0.10
1 50K Trimpot $0.15
1 47ohm Resistor $0.01
1 LED $0.08
1 Proto Board or You can etch A PCB
1 3 volt power source battery, wall wart, whatever

Step 2: Learn the Layout

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12v water sensor.bmp
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Read Circuit Diagram

Step 3: Create PCB (skip step if using Proto board)

Picture of Create PCB (skip step if using Proto board)
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The Schematic is made with ExpressPCB which is a free PCB Layout Software you can download it here
Than Download the PCB file and open and print it and make your PCB. Here are a few links to Instructibles that show you how to make a PCB
water sensor.pcb is 3v
water sensor2.pcb is 12v
5pcb
Cheap and Easy Toner Transfer for PCB Making
The Saltwater etch process

Step 4: Build It

Build time will update once I make the PCB

Step 5: Connect to HHO Cell or Any other Water Sening Probe

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Here are some mock ups of how to connect it to a HHO Cell or just detect water.

Step 6: 12 VOLT CIRCUIT

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Here is how to setup the circuit to run on 12 volts from a car battery the circuit is still the same just some resistors are added to the probes to protect the transistor and a larger resistor to protect the LED
Wayne TheS2 months ago

Thanks....the video saved me from pulling my hair out. Was not aware in re: tying the pot half to ground. I intend to use this as an auto switch on my bilge pump. I intend to add a three way switch, Off, Auto, Manual. I assume I will need to amp up the output to pull in a micro relay? If I am not mistaken the relay will require about 60 ua ....have not gotten it in yet to see. Any suggestions? Thanks for a great vid.

Cyberscann54 (author)  Wayne TheS2 months ago

I could see replacing the LED with a relay most relays are designed to operate from low voltage sources and switch on or off a high voltage supply so just remove the LED and its resistor and put a relay in there place and I'm guessing this is for a boat so powering it should be easy with no changes to the circuit since boats use a 12v system the circuit was designed for 12v you just need a 12v relay that can handle the pump. Thank you for the comments and good luck.

Thanks for the info...For anyone else interested, I will also be including a delay off timer of 10 secs or so in order for the water level to fall well below the probes and prevent an On/Off/On/Off scenario from wave action etc. The probes will be mounted about a 1/4" above the highest point of intake of the pump...this should allow the pump time to lower the level to the point of cavitation and then shut off....leaving the probes well out of the water.
Cyberscann54 (author)  Wayne TheS2 months ago

well since you want a delay timer a 555 or 556 chip can be used and the sensor can also be built from it if you want I can design the circuit for you and all you will need to do is get the parts and build it just let me know if you want me to do it

That would be great! Keep in mind that I am new to electronics (66 yrs old) so I do well with pictures :) I have plenty of 555 and 556's as well as ATTiny 13 and 85's as well. I have managed to struggle through burning the Tiny's with an Arduino ISP. I am thinking a delay off of about 45 sec, with the probes about 1/4 above the intake should give the pump enough time to drop the level well below the probes. Thanks for any help. BTW...the detector circuit works flawlessly but I would never have figured it out without your vid...which was outstanding.

eng_tako4 years ago
thank you very much you help me alot
Assuming clean water, zero turbulence, very small inflow related to volume, could I get 1/32 inch level gage accuracy? In other words, under perfect conditions, what accuracy could one expect?
Zhelnot4 years ago
are you done with this thing??
geniusgippy4 years ago
can nybody eloborate on which HHO cell to use!!!
jpsailr5 years ago
After many attempts to make a circuit like this, I gave up. Reason: when current flows through water from one plate to another, gas builds up on the sensor plates and the conductivity of the water reduces until it is undetectable, over 10 megohms within minutes. So if you're not there right when it happens, you will miss it. I solved this by creating a circuit which would put an AC current on the sensor plates. This continually purges the plates of gas and keeps the resistance through the water to less than 100 Kohms - very useable. This test ran for over 4 hours with no loss of conductivity. Now I successfully use it to detect bilge water as soon as it happens, or water on the basement floor. I will submit a project when I get it written up.
mathew0865 years ago
Hey... I find this one soo interesting n simple that i am planning to try oit put once. but i have a small question? How much current does the circuit consume for one time function. meaning if the circuit detects water how much currents is consumed by the circuit from the 12 V battery??? thanksss
That's pretty easy to figure out with Ohm's Law. There are two paths that current will take through the circuit: the first is through the LED and into the collector of the transistor, and the second is through the probes, the water itself, and the 22K resistor. The current through the LED part of the circuit will be about 36mA, and assuming the water has perfect conductivity (it definitely doesn't, but that's a worst-case scenario) the current through the probes will be under 1mA. In other words, trivial.